Surprise is a brief emotional state that is the result of experiencing an unexpected relevant event. Surprise can have any valence; that is, it can be neutral, pleasant, or   unpleasant
Spontaneous, involuntary surprise is often expressed for only a fraction of a second. It may be followed immediately by the emotion of fear, joy or confusion. The intensity of the surprise is associated with how much the jaw drops, but the mouth may not open at all in some cases. The raising of the eyebrows, at least momentarily, is the most distinctive and  predictable sign of surprise